The Liberal Democrats have voted to accept nuclear power, in a historic reversal of their long-held opposition to atomic energy.

Party members backed nuclear power as long as it is not subsidised, after several hours of tense debate at the Glasgow autumn conference

Ed Davey, the Liberal Democrat energy secretary, urged his colleagues to support nuclear power, saying it would be "reckless" to reject such a major low-carbon source of energy that is needed to tackle climate change.

He argued against nuclear power at the party's conference in 2006 but has listened to arguments about its low-carbon benefits since then.

"I've changed my mind because of climate change," he said.

It would be "unimaginably" hard to create a zero-carbon Britain without getting electricity from nuclear, Davey said.

The motion backed by the party was "option B", accepting that in future nuclear power stations could play a limited role in electricity supply, in a safely regulated environment and without allowing any public subsidy. They rejected "option A", ruling out the construction of a new generation of nuclear plant.

There were strong feelings on both sides that split former political allies. Joel Kenrick, an ex-adviser to Chris Huhne when he was energy secretary, argued in favour of allowing nuclear power to tackle climate change.

But Huhne's other former adviser, Duncan Brack, said the party's idea of allowing limited nuclear without subsidy is a "chimera" because it would be impossible.

Many others argued that abandoning the party's long-held opposition to nuclear power would risk alienating core voters.

The party also backed the controversial practice of fracking for gas, which critics claim can damage the environment and rural landscapes. It supported shale gas drilling in "controlled" circumstances.

Nick Clegg has already publicly given his backing many times to the idea of nuclear power without subsidy, so the motion is only confirming that the party's members back his stance.

Davey is already deep in negotiation with EDF, the French energy firm, about how much extra it can charge people for electricity to cover the cost of the construction of new nuclear plants.

Craig Bennett, policy director at Friends of the Earth, said it "punches a huge hole in the Liberal Democrats fast-sinking green credibility".

"Nuclear power comes with massive costs attached," he said. "Ed Davey is deluded if he thinks new reactors can go ahead without public subsidy – building them will result in the Liberal Democrats, yet again, breaking their promises."

Dr Doug Parr, chief scientist at Greenpeace, said the vote "shows how far the Liberal Democrats have slid from their previously principled position on energy and climate".

He added: "The party now seems prepared to thrust the issues of nuclear waste and funding on to future generations, rather than take on vested interests and put us on the road to dealing with the climate crisis in a clean, safe way."